Metal-separating device



Jan. 7, 1964 I H. G. KRESTIN ETAL 3,117,080

METAL-SEPARATING DEVICE Filed 001;- 31, 1961 2 Sheets-Sheet 1 AMPLITUDE INVENTORS HANS GEORG KRESTIN ALBERT SEIDL Jan. 7, 1964 H. e. KRESTIN ETAL 3,117,080

METAL-SEPARATING DEVICE Filed Oct. 31, 1961 2 Sheets-Sheet 2 United States Patent F 3,117,080 METAL-SEPARATING DEVICE Hans Georg Krestin, Wolf ang, near Hanan, and Albert Seidl, Kalil (Main), Germany, assignors to Farbwerke Hoechst Airtiengesellschaft vormals Meister Lucius 8: Briining, Frankfurt am Main, Germany, a corporation of Germany Filed Get. 31, 196i, Ser. No. 149,065 Claims priority, application Germany Nov. 3, 1960 2 Claims. (Cl. 209-1) The present invention relates to a device separating metallic substances from grinding material or the like as they move through the device by gravity.

German Patent 929,046 describes a device for separating metallic substances from material to be ground by flowing material to be ground through an electro-magnetic alternating field produced by means of one or more coils and extending over the interior of a shaft, and a mechanical separating means, for example a flap, actuated by means of an amplifier. The amplifier comprises means to rectify and differentiate the voltage disturbance produced by a substance passing through the magnetic field and amplified by the coil or coils when metallic substance passes therethrough. The amplifier also includes time constants means to delay operation of the separating means, for a period of time corresponding to the time it takes for the material to be ground to pass from the coil or coils to the separating means.

This device substantially constitutes a sensing head comprising a vertical shaft carrying at its upper end a sensin-g coil with an oscillator. The material to be ground passes through the high frequency alternating field of the sensing coil. The lower end of the shaft is provided with a deflecting flap for temporarily deflecting the flowing material to be ground. The deflecting fiap is actuated as soon as metallic substance included in the material to be ground is detected by the sensing coil. This is due to the fact that substances, whether ferro-magnetic or not, which enter into an oscillator-produced alternating field of high frequency produce alterations in this field both as regards to amplitude and the frequency of the oscillator. Such effect is especially more pronounced in metals than in non-metals.

If material including metallic substance is passed through the high frequency alternating field produced by the oscillator, the anode current of the oscillator tube will undergo impulse-like alteration.

The oscillogram of such impulse-like alteration of the anode current produced by the oscillator is shown diagrammatically in the accompanying drawing (cf. FIG. 1) which illustrates that this impulse comprises a fundamental oscillation with a frequency lower than 56 Hz. and various harmonic oscillations. The oscillation lower than the 50 Hz. frequency represents a considerable portion of the impulse. When the impulse is amplified, the line disturbing voltage of 50 HZ. induced in the search coil is also amplified. Compensation of this line disturbing voltage of O Hz. in the amplifier also weakens the impulse produced by the metallic substance. Other high frequency disturbances introduced into the device via the search coil can be screened out in the amplifier, since their frequency is substantially higher than the impulse frequency.

The present invention provides a device for separating metallic substance from grinding material as described above, but additionally equipped with means to avoid weakening of the impulse produced by metallic substance by compensation in the amplifier and comprising a sensing head with at least two shafts, each shaft carrying a sensing coil. The sensing coils of each two shafts may be counter-connected (in reverse order) one with the other, whereby any disturbing volt-age induced in both 3,117fi3d Patented Jan. 7, 1954 of the two coils is compensated and neutralized without weakening the high frequency field of the oscillator. The two sensing coils each have the same number of windings. The counter-connection comprises connecting the head or upper end of the first coil to the opposite or lower end of the second coil and, inversely, the lower end of the first coil is connected to the head or upper end of the second coil. This involves compensation of any external disturbing field and the disturbing voltage U is found to be equal U Metals cause a very pronounced disturbing impulse whereas non-metals may create such impulse only in that case where material to be ground is introduced batchwise into the search coil. In batchwise introduction of the material to be ground into the search coil, actuation of the device, and more especially the deflecting flap, can be avoided when a batch is introduced according to this invention by using a sensing head (detecting mechanism) designed so as to form two shafts disposed side by side, with each of these two shafts carrying a sensing coil counterconnected (in reverse order) one with the other and arranged at different heights with respect to the two shafts, and advantageously staggered by at least the width of one coil.

This arrangement permits distributing the flowing material into the two shafts. An impulse formed by batchwise introduction is weakened due to the material being distributed between two shafts. In other words, two impulses are produced one after the other with respect to time. The amplitude of each of these impulses is substantially smaller than the amplitude of the impulse that would be produced if the whole material were passed through one shaft.

Referring to the accompanying drawing:

FIG. 1 represents the oscillogram of an impulse-like alteration. FIG. 2 and FIG. 3 represent an exemplary device of the invention with two shafts. FIGURE 4 is a perspective VlBW of an apparatus incorporating the present invention and showing the flap and actuating mechanism for separating material.

The metal-searching device comprises more especially: an inlet opening 1 for the material to arrive in the sensing head with the two shafts 2 and 2'; two sensing coils 3 and 4 having the same number of windings and disposed on shaft 2 and shaft 2, respectively; and an oscillator 5 connected with oscillator coils 3 and i, the head end of coil 3 being connected with the tail end of coil 4 in the direction of flow of material through the shafts 2 and 2' and the head end of coil 4 being connected with the tail end of coil 3.

This arrangement enables the formation of high frequency fields 6 and 7 which are affected by the passage of metal through the shaft. On the other hand, any field which will disturb the effect produced by the coils is neutralized by the coils, due to the connection of the ends of the coils in reverse order and the disturbing voltage U is found to be equal U However, when metal passes through the sensing heat it will reduce a voltage in the coil 3 or 4 which is used as a signal to operate the responsive device, for example, a flap. The flap is actuated by the signal as a valve to separate the material containing metal from the other material being processed.

One form of responsive device is illustrated more in detail in FIGURE 4 as comprising a chamber 8 into which the material flows by gravity as it leaves the plurality of shafts 2 and 2.. The deflecting flap 9 of the responsive device is mounted at one edge of a rock shaft 19 pivotally mounted in the chamber. in one position the flap 9 directs material flowing from the shafts 2 and 2 and chamber '8 through the outlet 12., and in its other position directs the material from the chamber through the outlet 13. For example, the outlet 12 may be for metallic substances While the outlet 13 is for grinding material.

We claim:

1. In a device including a flap for separating a material free from metallic substances from a feed stream of material containing both nonmetallic and metallic substances Which comprises, a sensing head having at least two shafts disposed side by side, each of these two shafts having a sensing coil disposed at different heights with respect to the two shafts with windings extending progressively along the shafts, and the upper end of each winding connected to the lower end of the other Winding to neutralize transient voltages impressed on the coils and 4 reduce the effect of variations in the flow of material through the sensing head.

2. The device of claim 1, wherein the sensing coils are staggered in height on the respective shafts by at 5 least the Width of one coil.

References Cited in the file of this patent UNITED STATES PATENTS 2,504,731 Rose Apr. 18, 1950 FOREIGN PATENTS 929,046 Germany June 16, 1955 

1. IN A DEVICE INCLUDING A FLAP FOR SEPARATING A MATERIAL FREE FORM METALLIC SUBSTANCES FROM A FEED STREAM OF MATERIAL CONTAINING BOTH NONMETALLIC AND METALLIC SUBSTANCES WHICH COMPRISES, A SENSING HEAD HAVING AT LEAST TWO SHAFTS DISPOSED SIDE BY SIDE, EACH OF THESE TWO SHAFTS HAVING A SENSING COIL DISPOSED AT DIFFERENT HEIGHTS WITH RESPECT TO THE TWO SHAFTS WITH WINDINGS EXTENDING PROGRESSIVELY ALONG THE SHAFTS, AND THE UPPER END OF EACH WINDING CONNECTED TO THE LOWER END OF THE OTHER WINDING TO NEUTRALIZE TRANSIENT VOLTAGES IMPRESSED ON THE COILS AND REDUCE THE EFFECT OF VARIATIONS IN THE FLOW OF MATERIAL THROUGH THE SENSING HEAD. 